On Coastal Jets and Upwelling in Bounded Basins

Abstract

The relationship between coastal upwelling and coastal long-short currents is studied in a simple model of a continuously stratified fluid in a closed basin on the f-plane. It is shown that the coastal long-shore current at any point on the basin's perimeter is determined primarily by the components of the long-shore stress with the largest long-shore scales, in particular from the perimeter average of the long-shore stress. In addition, the depth structure of the upwelling itself is shown to be dependent on the long-shore scale. It is concluded that the relationship between upwelling and long-shore currents is non-local, that mass balance is not achieved locally in planes normal to the coast, and that the relationship between onshore flows and long-shore currents is scale-dependent. An intrinsic long-shore length scale is found separating two regimes of flow with distinctly different relations between the wind stress, onshore, and long-shore flows. Since both regimes are present simultaneously for a wind stress containing a variety of long-shore scales, the determination of the long-shors structure of the wind stress is essential to an understanding of the local oceanic upwelling and long-shore current structure.